A manufacturing machine for producing combination cigarette filters comprises a group-forming unit that forms groups of filter portions, each comprising at least two different filter portions aligned axially and contacting at the ends; a wrapping unit which receives a succession of groups of filter portions from the group-forming unit, wraps a strip of wrapping material about the succession of groups of filter portions to form a continuous filter rod, and cuts combination filters from the continuous filter rod by cyclically cutting the filter rod transversely; and a transfer unit which transfers the groups of filter portions from the group-forming unit, in which the groups of filter portions travel transversely (i.e. perpendicular to their central axes), to the wrapping unit, in which the groups of filter portions travel axially (i.e. parallel to their central axes).
The group-forming unit comprises a frame that rests on the floor and supports a number of structurally identical feed stations, each for supplying respective filter portions to form the groups of filter portions. Each feed station comprises a top hopper housing a mass of respective filter portions; a number of cascaded drums, the first of which withdraws the filter portions successively from the bottom of the hopper; and at least one insertion drum, in which the filter portions received from the end drum of said number are inserted into respective groups of filter portions.
Examples of group-forming units of manufacturing machines for producing combination filters are to be found in EP0383970A1, EP1016350A2, U.S. Pat. No. 3,357,320A1 and U.S. Pat. No. 4,237,778A1.
To meet changing market demand, a modern manufacturing machine must be able to produce a range of combination cigarette filters, which means brand changes are relatively frequent to change the machine over to the manufacture of a different type of combination filter. Very often, the new type of combination cigarette filter calls for using filter portions of a different size/composition, so the brand change calls for changing some or all of the operating parts of one or more feed stations. Changing some or all of the operating parts of a feed station is a complicated, time-consuming job, both to dismantle the existing operating parts, and above all to assemble the new parts. Dismantling the existing operating parts may be time-consuming and complicated by access to the feed station being hindered by the adjacent feed stations; whereas assembling the new parts is always time-consuming and complicated, on account of the necessity, once the new operating parts are connected mechanically (which in itself is done fairly quickly), to calibrate/adjust the new parts so they interact properly.